In German patent application P 42 21 185.9 it has already been proposed to generate, by punching or electrical discharge machining (EDM), spray openings in perforated spray disks. The spray openings possess a non-cylindrical shape after an additional process step involving partial deep drawing of the perforated spray disk. In this known perforated spray disk, the spray openings are first produced vertically and cylindrically in a flat piece of sheet metal by punching or electrical discharge machining. In a subsequent process step a central region of the perforated spray disk, in which the spray openings are located, is plastically deformed by deep drawing, causing the central region of the perforated spray disk to take on a domed shape. The result of the deep drawing is that the spray openings are stretched farther out downstream than upstream, so that truncated conical flares of the spray openings are produced.
In addition to DE-OS 38 01 778 mentioned above, it is also already known from U.S. Pat. No. 4,080,700 to use flaring spray holes in a spray plate. The spray holes produced in the spray plate each have a triangular cross section; the triangles being approximately equilateral. After the spray holes are produced, the spray plate is domed with a punch, so that as a result the spray holes flare out in the direction of motion of the punch, since the spray holes are stretched farther out downstream than upstream. Thus at least two mutually independent manufacturing methods are needed to achieve this configuration of the spray holes. The flares of the spray holes cannot be completely symmetrical over their entire length because of the doming of the spray plate.
Since the central region of the perforated spray disk is domed, at least one spray opening is inclined with respect to a lengthwise valve axis, and the truncated conical flare is not necessarily completely symmetrical over the entire length of the spray opening. The spray openings are therefore produced in an unflared shape, and only expanded downstream by an additional process.
Moreover, it is also known from DE-OS 38 01 778 to use for fuel injection valves a diaphragm made of a material with great natural hardness, for example monocrystalline silicon, whose fuel discharge openings are produced by etching. In order to produce contours for the fuel discharge openings which deviate from a cylindrical shape, another complex and costly treatment with high-energy radiation, e.g. laser radiation, is used after the etching step.